In a conventional liquid manure system, manure is delivered by barn cleaners or other conveying apparatus to a below-ground pit adjacent the barn or other livestock feed area. In a conventional system, a pump is located in the pit and acts to selectively mix or homogenize the manure slurry and to deliver the mixed slurry from the pit. In the homogenizing mode of operation, the pump is raised and lowered in the pit and rotated so that the discharge of the pump is directed to all areas of the pit to mix or homogenize the liquid manure slurry. When it is desired to discharge the slurry from the pit, the pump is lowered to a position where the outlet of the pump is automatically connected to a discharge pipe and operation of the pump will then discharge the liquid manure slurry through the discharge pipe to a liquid storage tank or other discharge site.
U.S. patent application Ser. No. 06/327,792, filed Dec. 7, 1981, discloses an agitating and pumping system for liquid manure slurry. In accordance with the invention of that patent application, the pump, which is located within the pit that contains the manure slurry, is operably connected through a vertical drive shaft to a motor, which is positioned above the pit and out of contact with the liquid slurry. The motor-pump unit is mounted for sliding vertical movement within the pit on a fixed column and in addition, can be rotated horizontally about the column. With this arrangement, as disclosed in the aforementioned patent application, the pump can be raised and lowered within the pit, as well as rotated, to thereby direct the discharge of the pump to all areas of the pit to thoroughly mix or homogenize the slurry.
In the aforementioned patent application, the motor-pump unit is raised and lowered through a cable arrangement in which a cable, wound on a drum located at the top of the column, passes over a pulley and is dead-ended on the fixed column. Through power operation of the drum, the motor-pump unit can be raised and lowered within the pit.
With the construction as disclosed in the aforementioned patent application, the motor-pump unit can be raised and lowered through a distance of approximately 6 feet and as the motor-pump unit has substantial weight, generally in the range of about 700 lbs., any malfunction in the system, such as breakage of the cable, can result in a free fall of the motor-pump unit over a substantial distance which could cause considerable damage to the pump or motor. Furthermore, in the event of cable breakage or when the pump is brought to rest, continued operation of the cable drum will result in the unwinding of the cable which can cause entangelment of the cable.